Not Applicable.
The present invention relates generally to an apparatus and method for the detection of the dispensing of a product from a vending machine, and in particular to, a fog-resistant optical detection system utilizing an infrared beam transmitted from an emitter, to a reflector, and back to a detector, the path of which is broken by a product as it is dispensed from the vending machine, thereby generating a detectable signal.
Traditionally, vending machines for canned or packaged goods include a sensing mechanism designed to detect the impact of a dispensed product or package deposited in a chute or bin, such as is shown in U.S. Pat. No. 5,927,539 to Truitt et al. for a modular vending machine with a dispensing detection device. Turning to FIGS. 1-3, a typical vending machine 10 is shown employing within a cabinet 11 a traditional dispensing detection device 12, of the ""539 Truitt et al. patent. The detection device 12 provides a receiving trough 14 that is defined by a number of detector plates 16 for downwardly directing a dispensed product to a receiving plate 18. In particular, each detector plate 16 includes a chute plate 20 which is opposed by a corresponding substantially parallel cover plate 22. The cover plate provides the support surface for a dispensed product as it is transferred from the storage columns 17 onto the receiving plate 18. In order to sense whether a dispensed product has passed over at least one of the detector plates 16, a membrane switch 24 and a force director 26 are disposed between the chute plate 20 and the cover plate 22. When the dispensed product passes over the force director 26, the membrane switch 24 closes, completing a circuit that registers that a product has in fact been dispensed.
These traditional impact sensors are sensitive to the impact of the falling product in terms of whether there is a soft or hard impact, with hard impacts being easier to detect. Lightweight products which result in soft impacts having lower forces are difficult to detect, and accordingly, traditional impact sensors must be capable of sensing impacts varying over a wide range of forces, often with a reduction in reliability for detecting the impact of lightweight products. In the event the dispensing of a lightweight product is not properly detected by a traditional impact sensor, the vending machine is likely to dispense a second product, or to xe2x80x9cdouble-vendxe2x80x9d, resulting in an error condition requiring a service person or route manager to take corrective action.
A further drawback with traditional impact detection systems arises where products are stored, and dispensed in xe2x80x9ctriple deepxe2x80x9d vending machines, as are commonly utilized with refrigerated canned products. Specifically, the time between the dispensing of a canned good from a first column and a second column of goods, or between a second column of goods and a third column is very small. A traditional impact sensor must be capable of registering the fall of the dispensed product rapidly, so as to immediately stop the vending machine drive motor from dispensing a product from the second or third columns of goods. Impact sensors capable of operating with the required speed and accuracy are difficult and costly to manufacture.
Alternative types of sensors to register the vending or dispensing of a product, such as photoelectric sensors, magnetic sensors, piezo-electric sensors, and optical or acoustic sensors are known, such as are disclosed in U.S. Pat. No. 4,359,147 to Levasseur and in U.S. Pat. No. 4,252,250 to Toth. However, an additional consideration when designing sensors for use in refrigerated product vending machines is the exposure of the sensors to moisture caused by condensation within the vending machine itself. Such exposure to moisture and condensation can interfere with the operation of specific types of sensors, in particular, optical sensors which rely on the detection of emitted beams of light to detect the presence or absence of a product.
Accordingly, there is a need in the vending machine industry for a low cost, highly accurate optical sensor capable of quickly registering the dispensing of a product, which is particularly suited for use in vending machines configured to dispense canned and refrigerated products wherein moisture and water vapor condensation may be present.
Briefly stated, the preferred embodiment of the present invention is a dispensed product detection system and method utilizing an optical beam crossing the path through which a dispensed product travels. A light emitter transmits a light beam across the product path to a low-loss reflector tolerant of beam misalignment, where the beam is reflected back to an optical detector located adjacent the emitter. As a dispensed product passes through the light beam between the emitter and the detector, the beam is momentarily broken, resulting in a change in signal intensity observed by the optical detector. The emitter, detector, and reflector are each configured with an anti-fog film transparent to the optical wavelengths utilized by the emitter and detector, to prevent water condensation thereon, and to prevent any associated signal loss or degradation.
The foregoing and other objects, features, and advantages of the invention as well as presently preferred embodiments thereof will become more apparent from the reading of the following description in connection with the accompanying drawings.